SF 



U. S. DEPARTMENT OF AGRICULTURE, 

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 102, PART I. 



B. T. (JALLOWAY. < 'hi, f of Bureau. 



SUMMARY OF RECENT INVESTIGATIONS 

OF THE VALUE OF CACTI 

AS STOCK FOOD. 



DAVID GRIFFITHS, 

Assistant Agrostologist, Farm Management Investigations, 
Bureau of Plant Industry, 



R. F. HARE, 

Chemist, New Mexico College op Agriculture and 
Mechanic Arts. 



Issued January 4, 1907. 




WASHINGTON: 

GOVERNMENT printing office, 

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U. S. DEPARTMENT OF AGRICULTURE, 

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 102, PART I. 

B. T. GALLOWAY, Chief of Bureau. 



3 o 7 



SUMMARY OF RECENT INVESTIGATIONS 

OF THE VALUE OF CACTI 

AS STOCK FOOD. 



DAVID GRIFFITHS, 

Assistant Agrostologist, Farm Management Investigations, 
Bureau of Plant Industry, 



R. F. HARE, 

Chemist, New Mexico College of Agriculture and 
Mechanic Arts. 



Issued January 4, 1907. 




WASHINGTON: 
government printing office. 

1907. 

T7" 



SEP 19 i§07 
D. ofD. 









CONTENTS 



Page. 

Introduction 5 

The samples of cacti analyzed 6 

Water content 6 

Ash content - 7 

Food value of different parts of the plant 9 

A balanced ration of prickly pear : 10 

Relative value of the three groups of cacti 12 

Common and scientific names 13 

Climatic requirements of prickly pears ■ 14 

The use of prickly pear in Mexico 15 

The species of cacti and their analyses 15 



ILLUSTRATION. 



Plate I. Nopal cardon (Opuntia streptacantha Lehm.), the most important of 

the Mexican prickly pears ,. 12 

102—1 



B. P. I.— 242. 

SUMMARY OF RECENT INVESTIGATIONS OF THE 
VALUE OF CACTI AS STOCK FOOD. 



INTRODUCTION. 

In connection with introductions, the improvement of species, and 
a general study of the economic relationships of native and intro- 
duced species of cacti the authors have jointly undertaken a somewhat 
critical comparison of the species of this group from a forage stand- 
point. In order to make the chemical work worth while it has been 
necessary to put the characterizations of the different forms and 
species in such condition that they are recognizable to others. This 
could only be done by the use of copious notes in connection with 
each, for names are of uncertain meaning and in many cases will be 
of uncertain significance in this group of plants for a long time to 
come. The chemical side of the investigations seems to be essential, 
for when these studies were begun there was but little literature deal- 
ing with the cacti from a forage standpoint. 

a In two publications of the United States Department of Agriculture (Bulletin 
No. 74 of the Bureau of Plant Industry and Bulletin No. 91 of the Bureau of Animal 
Industry) the value of the cacti as forage plants has been demonstrated. Since these 
plants are known to possess important economic value more knowledge concerning 
them is desirable. As a basis for futiue investigations, the Bureau of Plant Industry 
and the Agricultural Experiment Station of New Mexico have collected specimens of 
these plants and their fruits froni a wide area, from which a large number of chemical 
analyses have been made. The results are detailed in the following pages, which 
contain 187 fodder analyses and 26 complete ash analyses. The territory from which 
the material was collected extends from central Texas to California and s outhward to 
the central plateau of Mexico. 

Attention is called to the fact that the apparent high content of fats and protein in 
the fruit of certain species is due to the large amount of these classes of nutrients found 
in the seed. As these seeds are surrounded by a dense layer of wholly indigestible 
tissue, the high content of ether extract and protein is misleading. The analyses 
show that the fodder value of the fruit of cholla (Opuntia fulgida) especially is little 
more than that of the stems. It will be seen that in chemical composition the different 
forms of cactus compare favorably with ordinary green fodders and root crops. 

There are many points of special interest in connection with the ash analyses, par- 
ticularly the high content of potash, magnesium, and calcium. Altho the cane cacti 
show a relatively higher food value, practical considerations relating to growth and 
ease of propagation render them of less value than the prickly pear, except in certain 
limited localities where they are especially abundant. — W. J. Spillman, Agriculturist 
in Charge of Farm Management Investigations. 

102—1 

5 



6 VALUE OF CACTI AS FOOD FOR STOCK. 

The investigations have been conducted in cooperation between 
the Office of Farm Management Investigations of the Bureau of Plant 
Industry and the Agricultural Experiment Station of New Mexico 
for the purpose of determining, if possible, the extent of variation and 
the nature of the food constituents of the different species which are 
likely to be utilized as food for stock. The plants are grouped under 
three general headings — prickly pears, cane cacti, and miscellaneous — 
the first group being by far the most important, tho the second is 
largely utilized in sections where its different representatives grow. 
Three or four members of this group have been fed to stock with 
more or less success. The third group consists of miscellaneous 
species from other cactus genera, which on the whole are but little 
utilized as stock feed, altho it is clearly shown that some of the species 
have been fed in rare instances. The interest in this group is largely 
a matter of comparison with the others. 

Details of the investigations are published in Bulletin No. 60 of 
the Agricultural Experiment Station of New Mexico. 

THE SAMPLES OF CACTI ANALYZED. 

Considerable importance is attached to the method of sampling, 
it being recognized that uniform samples of such succulent and vari- 
able plants are difficult to secure. It appeared more logical, there- 
fore, to describe the samples in such a way as to give other investi- 
gators and the reader an accurate idea of the portion of the plant used 
in the chemical analysis. The sample is indicated by a formula — 
for example (2-1-4-3-5) 3 — in which the left-hand figure indicates 
the number of terminal joints, the second number from the left the 
number of joints next to the terminal joint, and so on, the figure 
outside of the parentheses indicating the number of plants from 
which the sample was collected. All samples were forwarded to 
the laboratory in tin cans from which a minimum of evaporation 
took place. They were prepared by first being sliced open, so as to 
expose a maximum of cut surface, and dried by artificial heat at a 
temperature of not more than 70° C. The spines were then singed 
off by a small flame of complete combustion, care being taken neither 
to deposit combustion products upon nor injure the specimens. In 
the analyses the methods of the Association of Official Agricultural 
Chemists were followed, with the exception of a few modifications 
in the determination of certain ash constituents. 

WATER CONTENT. 

A collection of samples for chemical analysis was begun in 1904, 
and a fairly complete set was secured during that year; but, owing 
to the uncertainty due to the analysis of single samples, these were 
nearly all duplicated in 1905, in most cases from the same localities. 

102—1 



ASH CONTENT. 7 

Fortunately there was a great difference between the rainfall during 
the months from January to March of 1904 and 1905. The effect 
upon the water content of the plants is fairly well illustrated in the 
different tables of analyses, altho no special effort was made to collect 
the samples for the purpose of showing this feature in detail. There 
are some apparent exceptions to the rule that the samples collected 
in 1904 contain more water than those collected in 1905; but this 
may be accounted for in some cases by the difference in the portions 
of plant collected or in other cases possibly by local conditions. 
The amount of water in the different samples analyzed varied from 
60.99 to 95.5 per cent. The miscellaneous group is relatively more 
succulent than either of the other two, the average amount of water 
being 87.88 per cent, while the prickly pears averaged 84.26 per cent 
and the cane cacti 78.47 per cent. As a rule, the fruit contained 
more water than the stems and the younger growth more than the 
older. 

The difference in the species in the field during a dry and a wet 
season is very marked, and even prickly pear has its limit of drought 
endurance. Experience in southern Texas demonstrates that it is 
much reduced in value during- very prolonged dry seasons, for it 
becomes tough and leathery. "Fat pear" is largely the result pf 
distention of the tissues by water. Some species, Opuntia fulgida 
especially, when a favorable moist season follows an exceptionally 
dry one, will absorb so much water that the fruits and young joints 
become ruptured by the excessive turgidity, and this often occurs 
with the fruit of nopal camueso and other cultivated Mexican species. 

ASH CONTENT. 

Plants grown in the arid and semiarid Southwest, where there is an 
abundance of soluble salts in the soil, are found to contain more ash 
than those grown in regions of frequent rainfall. The cacti are cer- 
tainly no exceptions to this rule. The average ash in the air-dried 
stems and fruits of the prickly pears analyzed amounts to 18.25 per 
cent, for the cane cacti 15.50 per cent, and for the miscellaneous group 
13.54 per cent, one sample running as high in ash as 33.8 per cent of 
the air-dried substance. These averages would be still higher if they 
did not include the ash of fruits, which always contain less ash than 
the stems. The average ash in the air-dried fruits of the prickly 
pears, for instance, is 13.21 per cent, which is 5.4 per cent less than is 
contained in an average of both stems and fruits of this group and 6.35 
per cent less than is in the stems alone. It is the seed which is espe- 
cially low in ash, the fleshy portion resembling the stem more closely 
so far as its ash content is concerned. This is brought out very 
forcibly in samples Nos. 8022a and 8022o, the former being the fleshy 

102—1 



8 VALUE OF CACTI AS FOOD FOR STOCK. 

portion and the latter the seed of Opuntia phaeacantha. The fleshy 
portion contained 25.60 per cent of ash, while the seed contained only 
1.77 per cent. 

The elements of the ash are present in about the same proportion as 
in the ash of other plants, except potassium, magnesium, and calcium, 
which are found in large amounts. It is probably the presence of 
these salts, coupled with the high water content, that causes cattle to 
scour when fed on an exclusive roughage ration of these plants. 

In the following table there is given a complete analysis of the ash 
of a few of the samples, together with the results of the analysis of a 
composite sample, and an average of all the ash analyses made. Com- 
plete ash analyses were made of 26 samples besides the composite, 
which was a mixture prepared by carefully igniting in a muffle two 
grams of the ash of each of the 187 samples of cactus analyzed. 

Table I. — Chemical analyses of representative samples of cacti. 



Scientific name of cactus. 



Locality. 



Date of 
collection. 



§5 



6255 

6331 
3000 
6699 
7515 



Opuntia fulgida 

Echinocereus enneacanthus . . . 

Opuntia macrocentra 

Cereus giganteus 

Opuntia lindheimeri 

Composite 

Average of all ashes 



Santa Catalina 

Mountains, Ariz. 

Eagle Pass, Tex.. 

Garfield, N. Mex.. 

Tucson, Ariz 

Encinal, Tex 



May 4, 1904 

May 10,1904 

July 11,1904 

July 28,1904 

Jan. 17,1905 



(6-6) 
Plant... 



(2-1-1)3 



P. ct. 

14.25 

17.78 
16.45 
15.75 
21.05 



19. 05 



P. ct. 

.74 

.26 
.62 
.17 
.14 
.38 
.40 



P. ct. 
1.65 

3.31 
4.27 
.44 
.29 
3.17 
2.40 



















Pure ash. 












ft 

a 






pi" 




bo 


g 

n 




T3 
03 
U . 


"2 

03^ 


5 
'3 ■ 

03^ 




t3 




CO 

o 


Scientific name of 
cactus. 




s 




o3 

o 




3 

QJ 
Pi 

3P 


03 


2o 


o 

_oft 


O 

m 

'£ 03 
3 O 

%■% 

3 >- 


O 


03O 

o 




n 

oj 



3 





o 

H- 1 


3 
C 



3 
< 


M 

PI 


■0 

3 

"3 
o 


3 

03 

O 

ft 


_3 

o 
m 


§2. 

'3 o 
m 


ft.2 

O o3 

A in 
ft 


3 

o 

s 


H 

03 *-> 

a 


"3 
+^> 
o 
Eh 






P.ct. 


P.ct. 


P.ct. 


P. ct. 


P.ct. 


P. Ct. 


P. ct. 


P.ct. 


P.ct. 


P.ct. 


P.ct. 


P.ct. 


P.ct. 


6255 


Opuntia fulgida . . 


0.21 


0.53 


0.09 


24.31 


8.10 


11.89 


0.00 


0.63 


2.54 


2.00 


1.33 


42.73 


94.36 


6331 


Echinocereus en- 
neacanthus. 


.31 


.13 


.09 


22.66 


5.07 


16.61 


.62 


.SO 


1.20 


2.35 


2.90 


42.63 


95.37 


3000 


Opuntia macro- 
centra. 


.53 


.00 


.56 


24.75 


8.25 


8.33 


1.57 


1.56 


2.14 


1.16 


.95 


44.80 


94.60 


6699 


Cereus giganteus.. 


.30 


.07 


.15 


31.64 


5.78 


6.66 


.00 


.37 


.88 


4.12 


3.32 


41.06 


94.55 


V515 


Opuntia lindhei- 
meri. 


.20 


.00 


.49 


26.71 


2.27 


14.22 


.35 


.43 


1.11 


1.15 


2.15 


49.12 


98.26 




Composite.. 


.36 


.31 


.83 


28.90 


6.85 


10.49 


.47 


1.90 


2.70 


1.94 


2.20 


33.76 


90.71 




Average of 


.31 


.24 


.36 


27.38 


5. 31 


9.71 


.42 


1.58 


1.39 


1.64 


1.84 


45.90 


95.75 




all ashes. 





























102—1 



a For explanation of formula, see page 6. 



VALUE OF DIFFERENT PARTS OF PLANT AS FOOD. 9 

FOOD VALUE OF DIFFERENT PARTS OF THE PLANT. 

The opinion is prevalent in southern Texas that the old woody 
stems of Opuntia lindheimeri fed there are much more valuable as a 
stock food than the younger growths. So firmly do many believe 
this that they practise cutting off and throwing away two or three of 
the terminal joints when feeding. In Mexico, on the contrary, the 
young growth is always fed; but there the species are commonly 
much larger and stouter, and the trunks are altogether too woody 
to be fed even if it were desirable to do so. The reasons for the opin- 
ions current in Texas are rather clearly brought out in the analyses. 
The younger growth has a relatively higher water content, and there- 
fore probably causes more scouring, which is the only evil influence 
overcome by a rejection of it. On the other hand, the old stems 
contain a much larger proportion of fiber and are really of less forage 
value. 

Guthrie, after comparing his own analysis of the stems of four 
Australian species with the analysis of fruits made by Wolf, concludes 
that the latter are of less forage value than the stems, because they 
contain a smaller proportion of nutritious substance and more crude 
fiber. Forbes, 6 on the other hand, concludes from analyses of Ari- 
zona cylindrical-jointed species that the fruits of these species are 
relished by cattle on account of their high ether extract (including 
fats) . Our analyses show that the ether extract is mainly a constit- 
uent of the seeds, and since these pass thru cattle undigested can 
contribute nothing to either the palatability or nutritive value of 
this part of the plant. That the seed is not digested is plainly shown 
in the case of Opuntia lindheimeri in many favorable seasons in por- 
tions of Texas. In the vicinity of Austin, in the early spring of 1904, 
there were numberless young plants springing up from cattle drop- 
pings in many of the pastures. They were fully as numerous in some 
situations as are the seedlings of the mesquite under similar condi- 
tions in favorable seasons in the river valleys of Arizona and on the 
plains of southern Texas. 

This applies to the genus Opuntia, to which belong the prickly 
pears and cane cacti. The seeds of the other group are very different 
in character. There is no doubt that burros, which commonly feed 
upon the fruits of the viznaga (Ecliino cactus wislizeni) , get a great deal 
of nourishment out of the seeds, which are very oily and easily masti- 
cated. It is interesting to note that No. 8170a {Opuntia fulgida) 
contains but little more food value in the whole fruit than is found 
in the pulpy portion alone, but in this sample most of the seeds were 
poorly developed or sterile. Other samples of fruit of the same 
species show an apparently greater food value. 

a Agricultural Gazette, New South Wales, 11: 671. 1900. 

b Arizona Agricultural Experiment Station, Annual Report, 15: 496. 1904. 

102-1 



10 VALUE OF CACTI AS FOOD FOR STOCK. 

Table II. — Chemical composition of the different parts of fruits of each. 



Num- 
ber 
of 

sam- 
ple. 


Scientific name of 
cactus. 


Part of fruit 
analyzed. 


Water. 


Ash. 


Pro- 
tein. 


Fat. 


Nitro- 
gen, 
freeex- 
tract. 


Fiber. 


Or- 
ganic 
mat- 
ter. 


8022a 


Opuntia pbaeacantha 
Opuntia phaeacantha 
Opuntia spinosior . . . 
Opuntia spinosior. . . 
Eclrnocactus wisliz- 

eni. 
Echinocactus wisliz- 

eni. 

Opuntia fulgida 

Opuntia fulgida 


Seed 


P. ct. 

7.26 
92.50 
77.74 
83.04 

8.59 

94.14 

82. 84 
87.17 


P. ct. 
1.75 
2.09 
2.97 
3.10 
3.09 

.96 

2.70 
1.58 


P. ct. 
6.07 

.20 

1.74 

.55 

10.92 

.63 

.63 
.47 


P. ct. 

11.41 

.07 

1.11 

.24 

15.46 

.06 

.51 
.27 


P. ct. 
23. 18 
4.63 
11.50 
11.74 
36.59 

3.05 

11.63 
9.66 


P. ct. 

50.33 

.51 

4.94 

1.33 

25.37 

1.16 


P. ct. 
90.99 


8022 b 


Pulp 


5.41 


8162a 
8162b 


Whole fruit. . . 
Pulp 


19.29 
13.80 


8173a 


Seed 


88.31 


8173b 


Pulp 


4.90 


8170a 
8170b 


Whole fruit. . . 
Pulp 


1. 69 14. 46 
. 91 11. 25 











It must be undertood that we have analyzed here but few fruits 
aside from those which are of more value for forage than they are as 
food for man. None of the cylindrical-jointed species and but few 
of the native prickly pears of the United States bear edible fruits. 

A BALANCED RATION OF PRICKLY PEAR. 

To determine in just what proportion cactus should be fed with 
other foods to produce a balanced ration, it is necessary to know the 
amount of digestible nutrients contained in the cactus, as well as 
those of the food or foods with which it is to be fed. This has been 
determined for most foods, but unfortunately there are as yet no such 
data for the cacti. It is hoped to be able soon to obtain the coeffi- 
cient of digestion for Opuntia lindheimeri. For the present, all that 
can be done is to assume this digestibility coefficient to be the same as 
that of some food as similar in chemical composition and properties to 
the cacti as possible. It is somewhat difficult to secure a green fodder 
very similar in character to cactus, but perhaps its digestion coeffi- 
cient will not be mist very far by assuming it to be the same as that of 
immature green corn fodder. By using the coefficient for this fodder 
the nutrients in Opuntia lindheimeri are found to be: Protein, 0.47 per 
cent; fat, 0.26 per cent; carbohydrates, 7.85 per cent. This being the 
case, cactus would have a nutritive ratio of 1:18, a ratio which 
according to the best authorities would prohibit its use alone for any 
feeding standard. The nutritive ratio for a standard ration varies 
from 1:4 to 1:12, depending upon the age, character, and kind of 
animal to be fed, as well as the object of the feeding; that is, whether 
it is desired to produce work, flesh, or milk. 

If the object of feeding is to produce milk, a cow giving a heavy 
yield of milk should, according to the best authorities, be fed about 
25 to 30 pounds a day of organic matter, containing from 1.8 to 2 
pounds of digestible protein, from 0.4 to 0.7 pound of digestible fat, 
and 11 to 13 pounds of digestible carbohydrates, making a nutritive 

102—1 



A BALANCED RATION OF PRICKLY PEAR. 11 

ratio of from about 1 : 5.5 to 1 : 7. If a cow requiring a ration of this 
kind should eat cactus alone, it would take 160 pounds to furnish the 
fats and carbohydrates and an additional 240 pounds to furnish 
sufficient protein, and since to avoid scouring a cow should prob- 
ably not be fed to exceed 50 or 60 pounds of cactus a day, it may be 
readily seen how impossible it would be for a milk cow to get even a 
one-sided ration from cactus alone. 

A ration of 40 pounds of cactus with 10 pounds of wheat bran and 
12 pounds of corn stover would furnish the nutrients in somewhat 
near the proper proportion. In a ration of this kind the cow would 
get 21.16 pounds of organic matter, containing 1.68 pounds of pro- 
tein, 11.82 pounds of carbohydrates, and 0.49 pound of fat, which is 
in a ratio of 1 :7.7. 

If a ration is desired in which the cactus is fed with dried brewers' 
grain and cotton-seed meal, it could be made by feeding 60 pounds of 
cactus with 14 pounds of brewers' grain and 1 pound of cotton-seed 
meal. In this case 20.58 pounds of organic matter are fed, containing 
2.85 pounds of protein, 10.38 pounds of carbohydrates, and 1 pound of 
fat. This ration would contain the nutrients in the ratio of 1 : 4.5. If 
this ration is considered too narrow, it could be widened to good advan- 
tage by feeding with it a small quantity of coarse, dry fodder, rather 
than by increasing the amount of cactus. 

A balanced ration of cotton-seed meal and cactus can not be pre- 
pared, for jf the meal be fed in just sufficient quantity to furnish the 
proteids it would necessitate the feeding of too much cactus to sup- 
ply the remainder of the carbohydrates. From this it must not be 
inferred that a mixture of these foods would not make a desirable 
ration; in fact, current successful practise has demonstrated that it 
will. For example, a ration of prickly pear and cotton-seed meal was 
fed to steers for one hundred and five days in a recent experiment 
conducted by the Bureau of Plant Industry at Encinal, Tex., with a 
gain of 1J pounds of flesh a day at a cost of only 3 J cents. Any 
ration of these two foods that would secure this gain each day would 
contain an excess of the proteids over an amount necessary for a bal- 
anced ration. Fortunately, however, an excess of proteids can be 
utilized in serving the function of the carbohydrates in the animal 
body, and this no doubt is what took place in the above experiment. 
Usually proteids are the most expensive foods for man and beast, 
and it is poor economy to substitute them for carbohydrates; yet 
such a condition is not uncommon in Texas cattle feeding, where 
cotton-seed meal is cheaper than other more starchy foods. 

102-1 



12 VALUE OF CACTI AS FOOD FOR STOCK. 

RELATIVE VALUE OF THE THREE GROUPS OE CACTI. 

On account of several practical considerations the prickly pears 
are of much more value than either of the other two groups. They 
are more numerous in the wild state, they adapt themselves to culti- 
vation more readily, make a more rapid growth, and are more readily 
propagated from cuttings, all of which are of vital importance in the 
economic use and handling of the crop. Practically all of the Mex- 
ican prickly pears are fed to stock to a greater or less extent, espe- 
cially those growing where fodder is the most scarce, but there is only 
one cylindrical-jointed species (Opuntia imbricata) which is used to 
any appreciable extent. The experience of the writers has shown that 
Cereus giganteus is readily eaten by cattle when chopped up, but 
they know of no actual feeding having been conducted with it on 
any commercial scale. Mr. C. R. Orcutt states that Echinocactus 
orcuttii, which is typical of a considerable group of species, is occa- 
sionally fed in Lower California. It is only in rare instances, how- 
ever, that any great quantity of feed can be secured from cacti, out- 
side of the genus Opuntia, and the greater part of the feed in this 
genus is produced by the flat-jointed forms. There are about five 
species in the cylindrical-jointed group which have been fed with 
some success. Opuntia imbricata, from Mexico, has been referred to, 
and in various writings the use of Opuntia arborescens , Opuntia spi- 
nosior, and Opuntia fulgida are mentioned. To these should be 
added Opuntia prolifera from the coastal region of southern Cali- 
fornia. These species constitute, without doubt, the best of the 
cylindrical-jointed group, and when extent of territory covered, suc- 
culence, and ease of propagation are taken into consideration Opuntia 
fulgida and Opuntia imbricata are probably the most valuable of 
this group. Opuntia arborescens has a decidedly valuable character- 
istic in that it extends farther to the north than any of the other 
economic species of any of the groups, and it is fed to a considerable 
extent in localities from southern Colorado southward. 

The use of these species, however, and, in fact, the extended use of 
nearly all the native species of this country and Mexico, presupposes 
artificial preparation. In dry seasons in southern Arizona, cattle feed 
upon the pendent bunches of fruits of the cholla (Opuntia fulgida), 
but it is done at a great sacrifice of comfort. The Texas pear 
(Opuntia lindheimeri) is grazed to a considerable extent by cattle, 
sheep, and goats without any preparation whatever, and even such 
thorny forms as cardon, shown in Plate I, are grazed by cattle in 
extreme cases. a 

a For further discussion, see Bulletin 74 of the Bureau of Plant Industry. 

102—1 



Bui. 102, Pt. I, Bureau of Plant Industry, U. S. Dept. of Aericultur 



Plate I. 




VAKTOUS NAMES OF CACTI IN USE. 13 

COMMON AND SCIENTIFIC NAMES. 

Considerable attention has been given to the popular names by 
which the various species are designated, especially the larger Mexican 
forms, but inasmuch as these are to be more fully considered in 
another publication now in process of preparation a full discussion of 
the subject is postponed. 

The chaotic condition of the scientific literature and the general 
imperfection of knowledge of prickly-pear forms have rendered it very 
difficult to properly name the species discussed. The purpose of the 
writers has been to present the exact status of their information, 
indicating a doubt wherever one occurs. The Engelmann species, 
which are largely United States forms, are comparatively easily deter- 
mined, in most cases thru a reference to the types in the herbarium 
of the Missouri Botanical Garden. In case of long-established species, 
however, it is absolutely impossible to correlate the specimens with the 
literature and determine what name belongs to the plant under dis- 
cussion. O-puntia tuna, for instance, has been paraded in literature a 
great deal, and to it has been assigned all sorts of species; but, as 
pointed out by Berger and Maiden especially, no one knows what the 
species is, and the writers know of no way by which its identity can 
ever be determined. 

Some species are referred to their proper genera only. Others 
are given common names besides, but the majority of them are given 
scientific names. All species receiving chemical analyses are repre- 
sented in our collections by specimens mounted upon sheets in the 
ordinary way or put up in boxes or in liquid. Many are growing 
in conservatories or upon one of the plantations maintained by the 
United States Department of Agriculture, while the seeds of many 
species have been widely distributed to those interested in the scien- 
tific and economic study of the group. The work is therefore well 
supported by specimens to which access will be had in completing in 
the future such naming as has not hitherto been undertaken. It was 
early recognized that good dry specimens were absolutely necessary 
for this work in order to make the chemical analyses and determi- 
nations of permanent value. 

Whenever a sample or set of samples represents a striking or con- 
stant variation it is treated separately in the text; consequently 
Opuntia lindlieimeri, for instance, appears several times under two or 
more headings. Each number or group of numbers is accompanied 
by a brief set of notes made in the field beside the plant when the sam- 
ples were collected, elaborated and perfected by subsequent experience. 
These are presented as field notes simply and not as full technical 
descriptions. This rather full set of notes, popular and scientific 
names, and, as a final resort, our specimens and photographs, will 
make it possible to easily verify the determinations of the writers. 

102—1 



14 VALUE OF CACTI AS FOOD FOE STOCK. 

CLIMATIC REQUIREMENTS OF PRICKLY PEARS. 

Prickly pears and other cacti are apparently inseparably connected 
in the public mind with drought and heat, but this conception of the 
requirements for their best development is far from perfect. Our 
driest deserts produce none of these plants in economic quantities, 
and the same is true of our hottest regions. Rather than say they 
are adapted to conditions of extreme heat and drought, it should be 
said that they thrive best in a region which has an equable tempera- 
ture and a considerable rainfall periodically distributed. There is 
certainly no region in the world where these plants grow naturally in 
such profusion as they do upon the plateau of Mexico, but this is not a 
hot county; neither is it excessively dry. It is very dry during a 
large part of the year. It is a desert as compared with eastern Texas, 
for instance, but it has a considerable rainfall during an average year. 
The rain falls mostly in the summer, and then the country looks like 
anything but a desert. The average rainfall at Zacatecas for the 
past ten years, as stated by Mr. Albert L. de Lautreppe, who has 
made a special study of the weather records of that city in connection 
with a business venture, is 31^ inches, but the average for the seasons 
from January to April and from October to December is only five- 
eighths of an inch to 2 J inches, while the average for the other months 
of the year is 3 ^ to 7 J inches a month. June, July, and August are 
the rainy months, having an average rainfall of 4| to 7J- inches each 
for the past ten years. 

While many species appear to be able to withstand high tempera- 
tures, they develop naturally in the greatest profusion where the heat 
is not excessive. The plateau of Mexico is a region with compara- 
tively equable climate. Some species thrive under extremes of 
heat. Opuntia lindheimeri is at home in the lower Rio Grande Valley 
of Texas and Chihuahua, and the closely related Opuntia engelmanni 
and Opuntia engelmanni cycloides thrive in southern Arizona, where 
the mercury often reaches 111 F. On the other hand, there are 
species which grow where the winter temperatures go to at least -40° 
F., but the plants are small and of no economic importance in them- 
selves except as they may be used to give a hardy character to more 
valuable species. The valuable species of the Mexican highlands 
thrive where the temperature falls to 14° F. in very rare instances. 
Usually the freezing point is only rarely reached here. During the 
past winter (1905-6) the mercury dropt' at the city of Zacatecas 
to 14° F., and many of the more delicate spineless forms, as well 
as the natives, were badly injured. No pear was killed outright, but 
the branches were frozen down for four or more joints. These rotted 
and dropt off, but the old trunks survived. Qpuntia lindheimeri, 
the common species of southern Texas, has been injured very severely 
within the memory of the present generation. It suffered some injury 

102—1 



SPECIES OF CACTI AND THEIR ANALYSES. 15 

during the winter of 1904-5. In the vicinity of San Antonio many 
of the plants droopt badly after the coldest weather, which regis- 
tered a temperature of 12° F. The majority of the plants straight- 
ened up again, but in many the distal joints dropt off as the result 

of freezing. 

THE USE OF PRICKLY PEAR IN MEXICO. 

In Mexico the use of the prickly pear is much more varied than in 
this country. There the established plantations are guarded from 
animal depredations either by rude fences or hedges of some of the 
tall columnar species of Cereus or the more spiny opuntias. The 
latter are planted thickly in borders around the more nearly spineless 
forms, which stock eat readily. 

All of the species are fed to stock indiscriminately. Whatever is 
available and can be spared is singed and fed to cattle. So far as 
observed, the durasnillo (Opuntia leucotricha) is preferred to all others. 
This is due to some extent to its small fiber content, but more espe- 
cially to its abundant delicate spines, which are singed off more 
readily than those of other species which have fewer spines. 

However, the extent of cattle feeding upon this kind of food is 
not so great in Mexico as one would suppose from the abundance of 
the material and the great extent of time during which the practise 
has been in vogue. The fact is that the average Mexican peon can not 
afford to feed to stock what he himself can use so profitably in other 
ways. The prickly pear is to him primarily an article of human 
food, and its place can not be taken by any other plant. 

The young joints as well are eaten by man in Mexico, and the 
dried stems and joints are used for fuel. Of course, this fuel is 
exceedingly poor, but it serves the purpose in that land where this 
commodity is exceedingly scarce. The feeding of cacti to stock, 
therefore, is a secondary consideration. The limbs which break 
off and such other portions of the orchard material as can be spared 
without seriously jeopardizing the tuna crop, together with such 
wild forms as are available, are fed to cattle. On some of the large 
haciendas, especially those devoted to maguey culture, the feeding 
of pear to work oxen during the grassless season is a regular practise, 
but then only wild forms are used. Over a large part of the Repub- 
lic, therefore, altho the prickly pears are much used for forage, their 
principal use is as an article of human food. 

THE SPECIES OF CACTI AND THEIR ANALYSES. 

In all, 67 species and varieties of cacti are discust, all of which 
have been analyzed chemically, some represented by as high as five 
samples. One hundred and eighty-seven fodder analyses and 26 
complete ash analyses have been made. The following brief table 
will illustrate the characteristic composition of representative 
samples, together with an average of all the samples. 

102—1 



16 



VALUE OF CACTI AS FOOD FOR STOCK. 



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